Date of Award

January 2023

Document Type


Degree Name

Master of Science (MS)



First Advisor

Andre Kehn


Capital trials introduce several emotional components beyond what occurs within a typical trial. Furthermore, in cases where a defendant’s mental state has been called into question, there is additional layer of bias and stereotyping toward the defendant, particularly when diagnosed with schizophrenia or psychopathy. Additionally, expert testimony frequently enters the court as mitigating evidence to persuade jurors against the death penalty, yet prior research has found mixed results regarding which types of experts are most effective. On the other hand, prior criminal record may be utilized as an aggravating factor, yet its scope in differing crime contexts, such as a capital trial, is unknown. In the present study, a jury-eligible sample was provided with a written capital case vignette with twelve differing conditions. The intent was to examine the effects of mental diagnosis, disclosure of prior record, and type of expert testimony on mock jurors’ perceptions of the witness and defendant. After reading the case materials, participants completed sentencing decisions and several measures to assess their perceptions and attitudes. Admission of a prior record was found to increase negative perceptions of the defendant. Neuroscientific expert testimony produced greater positive perceptions of the witness. However, neither a diagnosis of schizophrenia nor psychopathy demonstrated a significant effect. Additionally, none of the manipulations were found to influence sentencing decisions regarding the death penalty. Furthermore, this study examined the role of mock juror attitudes, such as need for cognition, need for affect, attitudes toward people with mental illness, and pretrial juror attitudes, on death penalty decisions. Two models were used to identify mock juror attitudes that served as significant predictors of sentencing decisions. Both the implications of the findings and limitations are discussed.